My favorite riddle is from Harry Potter. It's Tom Riddle.
Ha... Ha... Okay, nevermind I'll go sit in my corner. Over here...
Okay, so in all seriousness, my favorite riddle is from Harry Potter, mostly because I haven't memorized that many riddles... But still, it's a good one! I'm sure a few of you have heard this before...
First, tell me the person who lives in disguise;
Who deals in secrets, and tells naught but lies.
Next, tell me what's always the last thing to mend;
The middle of middle, and the end of end.
And finally, give me the sound often heard,
During the search for a hard-to-find word.
Now string them together, and answer me this;
Which creature would you be unwilling to kiss?
Anyone? Anyone?
Also, my other two favorite riddles should be known to you guys. And they're just my favorites because I love who says them. Oh, and also because, they're actually pretty cool and well-worded.
To retrieve your missing Elements;
Just make sense of this change of events.
Twists and turns are my master plan;
Then find the Elements back where you began...
*facehoof* Seriously, Twi, how did you not get that one?! He was kinda being obvious.
Aaaand...
A weighty choice is yours to make;
The right selection, or a big mistake.
If the wrong choice you choose to pursue;
The foundations of home will crumble without you.
Now that I think about it, Discord didn't lie in this riddle either... He told RD that if she chose the wrong option, the 'foundations of home will crumble without you.' And they did! She chose to leave her friends, and Ponyville, RD's true home, was thrust into chaos. Discord... never really lied... That's cool. That adds some dimension to his character.
Okay, I got off topic. These are my favorite riddles!!!